Humboldt State University
Robert A. Paselk Scientific Instrument Museum
Chemical Heritage Foundation
This instrument illustrates the new features Zeiss introduced around 19262, and which charecterized their standard refractometer, with only cosmetic changes (e.g. knob size, knurling pattern, smooth vs. square edges), until they introduced their "new design" in 19503. Compared to the previous design (see the 1920 example in this exhibit), the instrument now has a rack and pinion adjustment for the alidade and prism, enabling more convenient and finer control in determination of the refractive index. The mirror has now been placed on an adjustable arm rotating about the prism axis, allowing greater control of the prism illumination (compare to the sliding mirror of the Spencer design). The mirror arm is locked in place with clamping scrrew riding in a slot in the support arm. The catalog scan is taken from the Fisher Scientific Company. Fisher Scientific 81. Pittsburgh (1926).
The Abbe refractometer provides a quick and easy means for determining refractive index and dispersion of liquids and solids. Its most common use is the determination of the concentrations of solutions. A brief essay, The Chemical Refractometer, describes the charecteristics, design, and use of these instruments. A detailed history, The Evolution of the Abbe Refractometer, traces the development of this valuable instrument to around 1980.
The instrument stands 11 1/2" high in the closed, vertical position. The round, cast iron base is 5 1/2" diameter. The curved edge of the base is black japanned, while the top is finished in a fine black crinkle enamel. The post is heavy cast iron, finished in crinkle enamel, and bolted to the base from below with three heavy screws. The logo is also engraved and black-filled on the telescope arm, along with the serial number: Nr.22661. The inlaid nickel silver scale has black-filled graduations to the thousands place, with numbering to the hundreds-place. The tenths-place is also numbered, with larger numerals (1,X) at the even-numbers, and is carried on a black japanned iron (or steel) arm. The alidade is black crinkle finished brass. The telescope, telescope arm and other furniture are nickel plated, while the prism holder/heating block has a flat black oxidized coating. The original knob for operating the prism holder has been replaced with custom machined handle. The exhibit includes a 1931 manual for this instrument.
The instrument is in its original light hardwood (alderwood) case (8 1/4 x 6 3/4 x 14" h), with a black painted iron carry-handle and a round nickel plated keyhole cover.
1 Nr. 22661 "was produced in January 20, 1926 and delivered to Carl Zeiss in New York in November 2., 1926." Personal communication (2003), Dr. Wolfgang Wimmer, Archivar, Carl Zeiss Jena GMBH.
2 The new instrument is illustrated in: Zeiss. Directions for using the Abbe Refractometer. 4th Edition (Mess. 172). Carl Zeiss, Jena (1926) pp 2 & 7; Fisher Scientific Company. Fisher Scientific 81. Pittsburgh (1926).
3 The Carl Zeiss document Reifezeit für High-Tech, under the column "Refraktometrie" has the following listing: 1950 neues Abbe-Refractometer.